Transcutaneous blood gas monitoring is known in the relevant arts as a method by which measurements of skin-surface gas pressures may be utilized to estimate arterial partial pressures of the gas of interest. In particular, skin surface oxygen or carbon dioxide pressure PO2 or PCO2, respectively, is measured by a locally applied, electrochemically based device in order to develop an estimate of arterial partial pressure of oxygen or carbon dioxide PaO2 or PaCO2, respectively. The obtained estimate is then made available to the clinician as an aid for the routine or emergency assessment of any of a variety of known cardiopulmonary functions.
In practice, a condition of hyperperfusion is indicated in the region of skin adjacent the applied device in order to enhance the flow of arterial blood gases toward and through the skin surface. To date, this hyperperfusion condition has been established by local heating of the skin with an electrode in order to distend the arterial capillaries. Unfortunately, such local heating carries with it an increased risk for tissue injury—erythema, blisters, burns and skin tears being among the documented complications. In addition, some debate exists within the art as to whether the increased local metabolic rate concomitant the application of heat counteracts the intended perfusion effect. If so, false readings may result, which may ultimately lead to inappropriate treatment of the patient.
The use of transcutaneous blood gas monitoring can be particularly advantageous when used in conjunction with negative pressure therapy for vacuum induced healing of open wounds or other tissue damage. Vacuum induced healing of open wounds has recently been popularized by Kinetic Concepts, Inc. of San Antonio, Texas. by its commercially available V.A.C.® product line. The vacuum induced healing process has been described in commonly assigned U.S. Pat. No. 4,969,880 issued on Nov. 13, 1990 to Zamierowski, as well as its continuations and continuations in part, U.S. Pat. No. 5,100,396, issued on Mar. 31, 1992, U.S. Pat. No. 5,261,893, issued Nov. 16,1993, and U.S. Pat. No. 5,527,293, issued Jun. 18, 1996, the disclosures of which are incorporated herein by this reference. Further improvements and modifications of the vacuum induced healing process are also described in U.S. Pat. No. 6071,267, issued on Jun. 6, 2000 to Zamieroweki and U.S. Pat. Nos. 5,636,643 and 5,645,081 issued to Argenta et al. on Jun. 10,1997 and Jul. 8, 1997 respectively, the disclosures of which are incorporated by reference as though fully set forth herein. Additional improvements have also been described in U.S. Pat. No. 6,142,982, issued on Nov. 7. 2000 to Hunt et al.
The use of transcutaneous blood gas monitoring in conjunction with V.A.C.® therapy allows for monitoring of blood gases within and around the wound bed. Blood gases can be an indicative factor of wound healing progression. Crucial information can be ascertained as to the progression of the wound without disturbing the wound dressing.
It is therefore a primary object of the present invention to improve over the prior art by providing a method and apparatus for the transcutaneous monitoring of blood gases wherein local heating for hyperperfusion is eliminated, thereby eliminating a significant patient hazard and wherein the concomitant metabolic effects of local heating are likewise eliminated, thereby reducing the likelihood for misdiagnosis leading to inappropriate treatment regimen.
Hyperperfusion through local heating also requires a prolonged warm up and stabilization time following electrode placement in order for equilibration and calibration of the electrochemical transducer. As a result, operator time is generally wasted in the administration of a transcutaneous blood gas evaluation. Additionally, transcutaneous blood gas monitors are either not available for emergency use or must be made available with an operated in a standby mode. Such a standby mode requires additional hardware and generally shortens the electrode lifecycle.
It is therefore a further object of the present invention to improve over the prior art by providing a method and apparatus for the transcutaneous monitoring of blood gases wherein the apparatus is available for full operation on short notice without requirement for additional and/or lifecycle shortening hardware.
It is still a further object of the present invention to provide a system and method that combines the advantages of a non-invasive blood gas monitoring device with the effectiveness of negative pressure therapy upon wounds, so as to further improve the efficacy of negative pressure therapy on the treatment of wounds and other tissue treatments.
Finally it is still a further object of the present invention to improve over the prior art by providing a method and apparatus for the transcutaneous monitoring of blood gases wherein the above-described objects are implemented without sacrifice to patient safety or device efficacy, but wherein unnecessary hardware and software is nonetheless avoided, thereby conserving the ever more limited healthcare dollar.